The invention relates to a method for enhancing an intelligent network service and to an intelligent network.
In telecommunications networks intelligence refers to the ability to access stored data, to process the data and to make decisions based on the data. Even the present telecommunications networks, such as the public switched telephone networks PSTN, are to some extent intelligent, since they are capable of processing stored data in routing a call, for instance. A typical ‘intelligent’ facility in present telecommunications networks is conditional call forwarding in which the call situation must be analysed and the call must be routed on according to the stored call forwarding service profile. Intelligent facilities of this kind have, however, so far been an inseparable part of the basic network and consequently, changing or adding facilities has required software updating, for instance, in all network switching centres.
One example of an intelligent network of this kind is described in the Q-1200 series recommendations of the ITU-T (International Telecommunications Union). The invention and its background is described using the terminology of the ETS 300 374-1 CoreINAP standard, but the invention can also be used in other intelligent networks implemented according to other intelligent network standards.
An intelligent network IN is a network architecture attached to a basic network (fixed or mobile network), which enables a swifter, easier and more flexible implementation and control of services. This is done by moving the control of the services away from the switching centre to a separate intelligent network functional unit. This way, the services can be made independent of the operation of the basic network, and the structure and software of the basic network need not be altered when services are changed or added. In an intelligent network, there can be several service providers in addition to the actual network operator.
The standardisation of intelligent networks has progressed swiftly during the last few years. These standards define a certain functional and hierarchical model for an intelligent network. In this model, the control of services has been moved from the switching centre of the basic network to a service control function (SCF) or a service control point (SCP) in the intelligent network. The service control function contains the service logic and any control related to the service (for instance the necessary database and service logic programs (SLP), in other words, the computer programs which implement the logical structure of a certain service, i.e. the service logic). The service control function can be a solely logical function which can be seen as uniform from the viewpoint of a service switching point SSP. It can be implemented in various ways internally, it can be distributed internally and the service logic related to it can be distributed into different nodes. The service data can also be distributed into other network nodes than the service logic. For instance, the service control function or point (SCF/SCP) can be distributed internally so that it only provides an open interface (such as CORBA, Common Object Request Broker Architecture) to an external server provided by an external service provider. In such a case, the SCP and the external server together form the service control function. Intelligent network services are designed, tested and deleted with special equipment called the service creation environment point (SCEP). A service management function (SMF) is used to manage the data relating to the users and the network in the database, including service-specific data and service programs. The service switching point (SSP) is typically a switching centre, a switching centre of the basic network, for instance, which executes a service switching function (SSF), i.e. identifies the intelligent network service and initiates interworking with the service control point SCP, but the SSP can also be a network element of another kind, such as the node responsible for the establishment of the connection in a VoIP protocol (Voice IP), i.e. a H.323 Gatekeeper. When a call including an intelligent network service is made, the service switching point SSP takes care of the connection arrangements. The intelligent network service is provided by initiating an intelligent network service when detecting detection points (DP) related to services, at which time the service switching point SSP requests instructions from the service control point SCP. In other words, the SSP hands over the control to the SCP and waits for operations from the SCP. When an intelligent network service is triggered at the service control point SCP, the service logic program SLP is initiated, whose operation determines the instructions which the SCP sends to the SSP in each call phase. The SSP interprets the received instructions and begins the call control functions required by them. Triggering an intelligent network service thus refers to the initiation of an intelligent network function due to an input created when a certain identification condition is met.
The above describes the present structure of intelligent networks. In this application, an intelligent network refers generally to a solution in which a node switching a call, a session or packet data contacts the service control function which provides the node in question instructions affecting the switching of the call, session or packet data. The contact between the node in question and the service control function is based on the service trigger data in the node. Triggerings, state models and a protocol providing controls or API interface between the control function and the network switching node characterize an intelligent network. Call, session or packet data switching can be described with a state model visible to the control function, the state model comprising phases and detection points associated with them, at which the processing can be interrupted to wait for instructions from the control function. Controls and operations can also be procedures directed at call objects and event notifications associated with them.
The services of an intelligent network are thus initiated at detection points defined by the basic call state model (BCSM) describing the operation of call control. The meeting order of the detection points is determined according to each call case. This is why services which are required in several different call cases must sometimes be defined to initiate at several different detection points. For instance, a service which reroutes a call in case of a failure must sometimes be set to initiate at detection points Busy, No_Answer and Route_Select_Failure. The above detection points are then set as trigger points. When the call control proceeds to one of these detection points, the service in question is initiated.
A problem with the above arrangement is that if in the case of the example given the service is initiated at the Busy detection point, for instance, the No_Answer and Route_Select_Failure detection points still remain active trigger points. If these detection points are detected later, it is possible that the same service is re-initiated in vain. Such a case is especially probable in the intelligent network according to the CoreINAP (Intelligent Network Application Protocol) CS3 (Capability Set 3) being developed in the ETSI (European Telecommunication Standard Institute) SPS3 work group and the ITU. According to plans, it will be possible for this intelligent network to have several controlling connections (MPC, Multiple Point of Control support) for one call state model to the service control point which correspondingly has several active service logic programs. It should be noted that the invention can be applied to an intelligent network according to any intelligent network standard (such as ANSI, AIN or WIN) providing MPC support. If the service logic programs activated for one call state model are completely independent, they have no knowledge of the services initiated by the others and thus may unknowingly re-initiate an already active service in vain.